In LTE (Long Term Evolution) , a radio base station eNB is configured to transmit/receive data to and from a mobile station UE performing communications in a cell under the control thereof, with a C-RNTI (Cell-Radio Network Temporary Identify) allocated to the mobile station UE as illustrated in FIG. 6 (see, non-patent document 1).
The C-RNTI is allocated on a cell-by-cell basis. In LTE, as illustrated in FIG. 6, a same C-RNTI cannot be allocated to a mobile station UE#1 and a mobile station UE#2 which perform communications in a same cell #A, and a same C-RNTI can be allocated to a mobile station UE#1 (or a mobile station UE#2) and a mobile station UE#3 which perform communications in different cells #A/#B.
Here, the C-RNTI is allocated in “Contention based RA (Random Access) Procedure” or a handover procedure.
In addition, the radio base station eNB is configured to assign resources for transmitting downlink data or uplink data by using the C-RNTI allocated to the mobile station UE.
Meanwhile, in the “Rel-12 workshop” of the 3GPP, many proposals on “Small cell enhancement” have been made as topics of FRA (Future Radio Access).
In such proposals, a concept of “Phantom cell” has been discussed.
As illustrated in FIG. 7, unlike a conventional macro cell, a phantom cell can cover a wider area by linking many “small cells” to form one large cell.